Preheat oven to 375°F (190°C). Clean mushrooms by wiping caps with a damp paper towel; avoid soaking. Remove stems by twisting and pulling; reserve stems for the stuffing. Arrange mushroom caps, cavity up, on a rimmed baking sheet or in a slightly oiled 9x13 baking dish.

Sauté reserved stems

Finely chop the reserved mushroom stems. In a skillet over medium heat, melt 1 tablespoon butter with 1 tablespoon olive oil. Add the chopped stems, 1/4 tsp kosher salt, and 1/8 tsp black pepper. Sauté 3–4 minutes until moisture has evaporated and stems begin to brown. Transfer to a bowl and let cool slightly.

Brush caps

Brush the outside and inside of mushroom caps lightly with the remaining 1 tablespoon butter. Sprinkle inside cavities with a pinch of salt and pepper. This helps release flavor and prevents caps from drying during baking.

Crabmeat Stuffing

Sweat aromatics

In the same skillet used for stems, add a small splash of olive oil if needed and reduce heat to low. Add the finely minced shallot and cook 2–3 minutes until softened but not browned. Add the minced garlic and cook 30 seconds until fragrant. Transfer shallot and garlic to the bowl with the sautéed stems.

Combine filling

To the bowl with stems, shallot, and garlic add crabmeat (checking for shells), softened cream cheese, mayonnaise, 1/2 cup grated Parmesan, 1/4 cup Panko breadcrumbs, 2 tbsp chopped parsley, Dijon mustard, Old Bay seasoning, lemon zest, lemon juice, and optional hot sauce. Gently fold components together with a rubber spatula until uniformly combined but crab pieces remain intact. Taste and adjust seasoning: add a pinch more salt, pepper, or lemon if needed.

Fill caps

Using a small spoon (or piping bag), mound about 1 to 1 1/2 tablespoons of the crab mixture into each mushroom cap, pressing gently so the filling contacts the cap cavity. Fill all 16 caps; if mixture runs short, divide evenly. Sprinkle the tops with the optional extra 2 tablespoons Panko and the extra 2 tablespoons grated Parmesan for a golden crust.

Bake & Finish

Bake the stuffed mushrooms in the preheated 375°F oven for 15–18 minutes, until the filling is bubbly and the tops are golden. If you want a deeper brown crust, broil on high for the last 1–2 minutes while watching carefully to avoid burning.

Remove from oven and let rest 2–3 minutes. Garnish with the reserved 1 tablespoon chopped parsley and a light squeeze of lemon over the mushrooms. Transfer to a serving plate and serve warm with lemon wedges on the side.

Storage: Leftovers can be refrigerated in an airtight container for up to 2 days. Reheat in a 350°F oven for 8–10 minutes until warmed through.